#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <errno.h>
#include <sys/time.h>
#include <unistd.h>
#include <time.h>
#include <getopt.h>
#include <sys/signal.h>
#include <termios.h>

struct watchdog_info{
    unsigned int options;   //options the card/driver supprots 19         
    unsigned int firmware_version;  //firmcard version of the card
    unsigned char identity[32];     //identity of the board 21
 };

#define WATCHDOG_IOCTL_BASE 'W'
#define WDIOC_GETSUPPORT _IOR(WATCHDOG_IOCTL_BASE, 0, struct watchdog_info)
#define WDIOC_SETTIMEOUT _IOWR(WATCHDOG_IOCTL_BASE, 6, int)
#define WDIOC_GETTIMEOUT _IOR(WATCHDOG_IOCTL_BASE, 7, int) 
#define WDIOS_DISABLECARD 0x0001        /* Turn off the watchdog timer */
#define WDIOS_ENABLECARD 0x0002 /* Turn on the watchdog timer */
#define WDIOC_SETOPTIONS _IOR(WATCHDOG_IOCTL_BASE, 4, int)
#define WDIOC_KEEPALIVE _IOR(WATCHDOG_IOCTL_BASE, 5, int)

int Getch (void)   //无回显的从屏幕输入字符，来达到喂狗的目的
{

     int ch;
     struct termios oldt, newt;   //终端设备结构体
     tcgetattr(STDIN_FILENO, &oldt);   //获得终端属性
     newt = oldt;
     newt.c_lflag &= ~(ECHO|ICANON);   //设置无回显属性
     tcsetattr(STDIN_FILENO, TCSANOW, &newt);  //设置新的终端属性
     ch = getchar();   //从键盘输入一个数据
     tcsetattr(STDIN_FILENO, TCSANOW, &oldt);  //恢复终端设备初始设置
     return ch;
}

 //suspend some seconds
int zsleep(int millisecond)
{
     unsigned long usec;
     usec=1000*millisecond;
     usleep(usec); //睡眠usec秒
}

int Init()
{ 
     int fd;
     //open device file
     fd = open("/dev/watchdog",O_RDWR);   //打开看门狗设备
    if(fd < 0)
     {
         printf("watchdog device open fail\n");
         return -1;
     }
     return fd;
}

int main(int argc,char **argv)
{
    int fd,ch;
    int i,j;
    char c;
    struct watchdog_info wi;
    fd=Init();  //打开终端看门狗设备
    //读板卡信息，但不常用

    ioctl(fd,WDIOC_GETSUPPORT,&wi);
    printf("%d,%s\n",wi.options,wi.identity);
    //读看门狗溢出时间，默认是5s

    //重新设置时间为10s
    i=5;
    printf("%d\n",ioctl(fd,WDIOC_SETTIMEOUT,&i));
    //读新的设置时间

    printf("%d\n",ioctl(fd,WDIOC_GETTIMEOUT,&i));
    printf("%d\n",i); 
    //看门狗开始和停止工作，打开和关闭设备具有同样的功能

    //关闭
    i=WDIOS_DISABLECARD;
    printf("%d\n",ioctl(fd,WDIOC_SETOPTIONS,&i));
    //打开
    i=WDIOS_ENABLECARD;
    printf("%d\n",ioctl(fd,WDIOC_SETOPTIONS,&i));
    while(1)
    {
        zsleep(100);
        if((c=Getch())!=27){
            //输入如果不是ESC，就喂狗，否则不喂狗，到时间后系统重启

            ioctl(fd,WDIOC_KEEPALIVE,NULL);
            //write(fd,NULL,1);     //同样是喂狗
        }
    }
    close(fd);   //关闭设备
    return 0;
}